Dual Plate Check Valve
Dual Plate Check Valves are automatic mechanical valves, which open with a forward flow and shut to a reversal inflow. The key feature of the check valve is to secure the mechanical devices in the pipe system by avoiding the reversing of the fluid. The swing check valve is an economic kind of check valve, but it has a higher slamming effect. Dual plate check valves are more common than swing control valves in various industries as they have a low slamming effect. In addition, the overall cost of the dual-plate check valve, which is the initial cost, operating cost, and energy cost, is well below the swing check valve.
What is Dual Plate Check Valve?
The concept of the Dual Plate Check Valve is the result of efforts to overcome issues associated with the traditional swing check valve and lift check valve. The Dual Plate Check Valve uses two spring-loaded plates mounted on the central hinge screw. As the flow reduces, the torsional spring movement closes the plates before the flow reversal takes place. This concept provides the dual benefits of No Water Hammer and Non-Slam at the same time. All the features taken together make the Dual Plate Check Valve the most powerful and efficient design. It is also known as SILENT CHECK VALVE.
Dual-Plate Check Valve Classification.
- By body structure.
- Retainer-less Constructionensures that they do not drill entirely into the valve body to allow the hinge-pin and the stop-pin to be fitted with a dual-plate check valve. Instead of drilling in, they’re going to machine a recess.
The retainer-less design with a dual plate check valve also ensures higher integrity at high pressure, ensuring little concerns about the leaking of the body.
- By end connection type.
- Lug: Lugged type flange contacts are similar to wafer but have slight variations. The lug holes are drilled and there is a lug hole for each bolt hole on the flanges. And each threaded hole has two bolts, one from each flange on opposite sides. This form of attachment can be used for dead-end operation, where there is just a flange on one side of the valve and the other is exposed to the environment, provided that the seat/retainer is screwed in place.
- Wafer: In the wafer attachment, the valve is mounted between the pipe flanges, and the bolts for the pipe flanges are attached to it. There are also some cantering holes on the body of some wafer forms to ensure the proper positioning of the valve between the flanges.
The wafer body type valve is the lightest variant of the body for installing between pipe flanges. Therefore, the wafer valve is cheaper than using other valves.
- Flange: The valve has a flanged end connection and bolt holes used to bolt the flanges on the shaft. Flanged attachments make it easier to remove and repair. Flanged attachments are popular in larger sizes of the valve. The gaskets must be used where these flanges come together.
- Butt Weld: The valve and pipe ends are of similar diameter. The exterior edge of both of them is machined to create a “valley” to be filled with welding metal. The two sections are welded around the rims as seen in the image. Butt welding connections are normally intended for smaller diameters, usually 2″ and below.
- By sealing method.
- Soft Seal: Soft seal means that one of the sealing pairs is constructed of low hardness materials. In general, the soft seal seat is made of non-metallic materials of a certain strength, hardness, and high-temperature tolerance to ensure zero leakage. However, service life and temperature adaptation are weaker than the metal seal valve. While some vendors have argued that their hard seal valve could produce zero leakage, the sealing of the hard seal valve is still weaker than the soft seal valve. However, the corrosion resistance of the soft seal valve to a certain corrosive medium cannot satisfy the technical requirements.
- Metal Seal: Both ends of the sealing pair are made out of metal or other metals of high hardness. So, the valve is considered a hard seal or metal to metal seal valve. Hard seal valve comes with low sealing but high-temperature tolerance, corrosion resistance, and mechanical characteristics are stronger than soft seal valve, such as steel + steel, steel + copper, steel + graphite, and steel + alloy steel. That may be cast iron, cast bronze, alloy steel, bead welding alloy, or spraying alloy.
How does Dual plate Check Valve work?
The valve plate opens when the fluid pressure flows in one direction. If the liquid flows in from the opposite direction due to fluid pressure and the impact of the plate on the valve seat, the flow will be cut off. The reduced flow would allow the torsion spring to close the plate without any reversal in fluid flow.
The valve has a cylindrical body and can have a much more linear stress distribution relative to the configuration of other valves. The cylindrical body is constructed to endure excessive weight, as well as the weight or thickness of the valve. Therefore, in the case of rigorous loading conditions, this valve has a distinct edge in terms of safety and economy.
Feature and Benefit of Dual Plate Check Valve.
The Dual-Plate Check Valve is a non-return valve that is comparatively stronger, lighter in weight, and compact in size than the conventional swing control valve or lift control valve.
- Pressure drop in a dual plate check is very low as compared to other check valves.
- Low wear and tear of the seat as it has a design of non-slamming type.
- Water hammers are almost negligible in dual-plate check valves because valve closure does not rely on backpressure and backflow. Each plate, which is half the size of a swing check disc, offers a straight flow path, providing the least resistance. As a result of spring-assisted closing, the valve closure begins as soon as the flow velocity decreases below the intended minimum velocity, and then the closing rate flows into the flow velocity reduction pattern. The valve shuts as the flow rate reaches zero and well before the flow is reversed. This reduces the water hammering.
- Non-Slam Design: The two plates in the Dual Plate Check Valve are mounted vertically in the middle for horizontal installations, completely removing the influence of gravity. Also, the momentum produced as they travel to a closed position is just a fraction of what is developed in a swing check valve. Further due to the spring-assisted closure, the valve shuts as the flow velocity reaches zero and until the flow reversal. When it begins to close, the flow, as such, cushions the plates and the seat, thereby reducing slamming.
Dual Plate Check Valve Application.
A dual plate check valve is the most suitable type of check valve that can be used for almost any configuration of material and system parameters used in various applications, some of the typical applications are:
- Water systems like boilers, Potable water, Fire safety system, Cooling & Heating water system, etc.
- Petrochemicals: Offshore/Onshore applications, LPG, LNG, Lube oil, Cryogenics, etc.
- Hydrocarbon: In almost all the applications.
- Air & Gas applications like Chlorine, Hydrogen, Nitrogen, Carbon Dioxide, Oxygen, Etc.
- Metallurgical and Chemical Applications: Sugar, Pharmaceuticals, Paper, Cement, Steel, Aluminium, Copper, zinc, etc.
Dual Plate Check Valve Installation Instructions.
- Cleaning the valve: The end connections of the Dual Plate Check Valves are secured by rust-proof oil. Clean the same thing before installation. Valve plates should be tested to verify that they are free of rust/oil.
- Checking the Direction of flow: The direction of flow in the line should match the direction of flow marked by the ‘arrow’ on the valve body and as indicated on the nameplate.
- Horizontal Piping: Insert the valve into the conduit such that the Pin Retainers (Plugs) are positioned up and down.
- Installation Distance between Check Valve and Butterfly Valve: When attaching the Butterfly valve to the outlet side of the Dual Plate Check Valve, ensure that there is sufficient space between the two valves so that the plates of the Dual Plate Check Valve are in an open position. Even, the Butterfly Valve disc does not touch the Dual Plate Check Valve. In addition, ensure adequate distance to prevent any peripheral or irregular flow conditions.
- The orientation of the valve to pump’s discharge: When fitting the Dual Plate Check Valve to the pump, attach to ensure that the pump flow follows the two plates of the valve for the better output.
- As a regulation, the valves are configured to operate in an optimally open state at a line flow rate of 2 to 2.7 m/sec of water for horizontal installations. The flow velocity for vertical installation can be marginally higher than for horizontal installation. For those fluids with less specific gravity, please specify at the time of the enquiry.
- Please refer to the manufacturing company for cyclic flow applications such as the outlet of reciprocating machines.
- Dual Plate Check Valves are advised to be mounted where the flow velocity around the cross-section is uniform.
Differences Between Dual Plate Check Valve And Swing Check Valve.
- Dual plate check valves are lightweight thus it is easy to handle while swing check valve is comparatively bulky thus it’s handling and support system is heavier.
- The structure of the dual plate check valve is compact with good design while the swing check has a complex body shape due to which it is difficult to assess stress points for critical applications.
- Dual plate check can be installed both in Horizontal and Vertical directions while swing check is suitable for horizontal applications.
- Due to its spring-assisted closure, a dual plate check can be installed for the flow upside down. This is not possible in the swing check valve.
- Pressure drops and energy losses are low in dual plate checks as compared to Swing checks irrespective of pressure ratings.
- A dual plate check has a non-slamming design while in swing check an external device is required to counter the slamming effect.
- There is negligible water hammering in dual plate checks compared to swing checks.
- Regular maintenance of seat and hinges is required in swing check due to impact loads and wear by rubbing. While dual plate check has a long life and a trouble-free operation.
Dual Plate Check Valve is also known as Zero Velocity Valve. The concept has all that the other traditional check valves are missing. It is the most effective valve in use, regardless of the fluid and service conditions, and the simplest to manage and can be fitted in any pipe structure without any restrictions.